The invention is based on a method for analyzing digital signals that are transmitted on a transmission frequency other than the one set on a radio receiver.
From the xe2x80x9cSpecifications of the Radio Data System (RDS) for VHF/FM Sound Broadcastingxe2x80x9d of the European Broadcasting Union, March 1984, it is known to transmit on the radio transmission frequencies not only radio programs in the context of the Radio Data System (abbreviated RDS), but also data in the form of digital signals. Some of these data are program identifiers (PI) associated with the transmission frequencies or with the programs transmitted on the transmission frequencies, which indicate which program is being transmitted on the respective transmission frequency.
German Patent No. 41 03 061 discloses radio receivers in which the program identifiers are used to locate receivable transmission frequencies which are transmitting the same program as the current transmission frequency. To check such alternative frequencies, the reception frequency of the radio receiver is switched over to the alternative transmission frequency for the duration of the check for an alternative frequency, i.e. to check its reception field strength and the program identifier PI associated with it. The resulting signal interruptions, in the range from 20 to 30 ms or 150 to 300 ms, are annoyingly evident in the form of crackling noises. It is therefore proposed to insert into the signal gaps substitute signals which are obtained, by buffering, from the audio signal segment immediately preceding the interruption, and thus to bridge the signal interruptions.
The method according to the present invention having contrast, the advantage that because of the short duration of the switchover from the current frequency to the frequency being checked, the audio signal interruption occurring during the switchover is inaudible. In addition, the outlay for recording the audio signal segment preceding the interruption is eliminated.
A development of the method ensures, by varying the time intervals and/or the durations Tu of the switchover from the current frequency to the frequency being checked, that the switchovers do not interfere with the auditory impression even in the event of possible human hearing sensitization effects.